New Data on Elusive Particle Shrouded in Secrecy

A team of physicists gathered in a room at CERN on Friday to begin crunching new data from the Large Hadron Collider this year. And they will be at it all week.

What they are seeing nobody knows.

What they are looking for is the beginning to the end of the longest and most expensive manhunt in the history of physics, one that has involved several generations of larger and larger particle accelerators: the spoor of a hypothetical particle that endows other elementary particles with mass. Known as the Higgs boson, it is the cornerstone of modern physics, but confirmation of its existence has eluded scientists for 40 years.

In December, scientists went into a qualified tizzy when two teams of physicists working on the Large Hadron Collider at CERN, outside Geneva, reported hints — but only hints — of a bump in their data that could be the boson.

The new data will show whether that was a fluke or whether they are really on the road to discovering the long-lost boson, physicists say. They are racing to make a deadline to report the results at the International Conference on High Energy Physics, or Ichep, in Melbourne, Australia, starting July 4.

This, all agree, is the boson’s last stand. If the December signal fades, it probably means that the Higgs boson, at least as physicists have envisioned it for the past 40 years, does not exist, and that theorists have to go back to their drawing boards.

If the signal is still there, the work is just beginning. In order for it to be certified as a “discovery,” there has to be less than one chance in 3.5 million that it is a fluke background fluctuation. Last fall’s signals were at the level of one chance in a thousand, which sounds good, but you would not board an airplane that crashed every thousand flights.

For now, the whole physics world is waiting and wondering.

Nobody who has seen the new data is talking, except to say not to believe the blogs, where a rumor of an enhanced signal has ricocheted around, and to warn that even if the signal is real, it may require much more data and analysis to establish that it actually acts like the Higgs boson and not an impostor.

“Please do not believe the blogs,” Fabiola Gianotti, the spokeswoman for the team known as Atlas, after its huge detector, pleaded in an e-mail.

For what it is worth, however, on the market prediction Web site Intrade, the price of a bet that the Higgs will be found before the end of this year zoomed over the weekend.

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Right now, most of the physicists doing the work do not even know what they have. In order to avoid bias, the physicists involved avoided looking at most of the crucial data until last week, when they “unblinded” it. About 500 physicists on each team are analyzing eight different ways a Higgs boson, once produced in the collider, might decay and leave its signature.

They all have to sign off on the final results, making for a very tight timetable.

“Our final Ichep results will not be even seen by the collaboration before the last day of June and then will require the usual final cosmetics for presentation,” wrote Joe Incandela of the University of California, Santa Barbara, spokesman for the team known as CMS, in an e-mail.

The particle is named for the University of Edinburgh scientist Peter Higgs, who was one of six physicists who suggested that a sort of cosmic molasses pervading space is what gives particles their heft. Particles trying to wade through it gather mass the way a bill moving though Congress gains riders and amendments, becoming more and more ponderous.

It was Dr. Higgs who pointed out that this cosmic molasses, normally invisible and, of course, odorless, would produce its own quantum particle if hit hard enough, by the right amount of energy, and so the branding rights went to him.

The current run of the Large Hadron Collider, which accelerates protons to energies of four trillion electron volts around a 17-mile underground racetrack at CERN, the European Organization for Nuclear Research, before banging them together into tiny fireballs of primordial energy, was designed to get the two experiments enough data so that they could each independently decide by the end of the year whether the Higgs boson exists.

Another possible hangup is that the two groups disagreed slightly last fall on the mass of the putative particle. The Atlas group put it at 124 billion electron volts, while the CMS group came up with 126 billion electron volts, in the units of mass and energy favored by physicists. By comparison, a proton weighs in at one billion electron volts and an electron at half a million.

If the discrepancy persists, it could undermine attempts to reach that statistical rigor.

Failure to find the Higgs would not be the end of the theory in which it is embedded, known as the Standard Model, which has passed every test for 30 years. But it would require physicists to go back to their blackboards for another method of imputing mass to particles.

Without such a mechanism, said Steven Weinberg of the University of Texas in Austin, who won a Nobel for using the Higgs theory to unify the electromagnetic and weak nuclear forces, the universe would be bleak. Elementary particles like quarks and electrons would be massless. “Atomic nuclei would still exist, but electrons would be massless, and so there would be no atoms,” he said. “And of course no life. Not even physicists.”

A version of this article appears in print on June 20, 2012, on Page A5 of the New York edition with the headline: New Data on Elusive Particle Is Shrouded in Secrecy. Order Reprints|Today's Paper|Subscribe